Resistor and method for making same

ABSTRACT

A resistor includes a substantially cylindrical resistive element having a resistance of less than about 1 mΩ, a substantially cylindrical first termination electrically connected to the resistive element and a second termination electrically connected to the resistive element. The substantially cylindrical first termination is hollow to allow for accepting a connection such as from a battery cable. In addition there may be sense leads present on the resistor. A method of forming a substantially cylindrical resistor includes forming a hollow cylindrical resistor body by rolling a flat sheet comprising a resistive element and a first termination and a second termination joined on opposite ends of the resistive element.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/280,230, filed May 16, 2014, issuing as U.S. Pat. No. 9,378,872 onJun. 28, 2016, which is a continuation of U.S. patent application Ser.No. 13/730,155, filed Dec. 28, 2012, now U.S. Pat. No. 8,730,003, issuedMay 20, 2014, which is a continuation of U.S. patent application Ser.No. 13/051,585, filed Mar. 18, 2011, now U.S. Pat. No. 8,344,846, issuedJan. 1, 2013, which is a divisional of U.S. patent application Ser. No.12/026,939, filed Feb. 6, 2008, now U.S. Pat. No. 7,911,319, issued Mar.22, 2011, the entire contents of all of which are hereby incorporated byreference as if fully set forth herein.

FIELD OF INVENTION

The present invention relates to resistors, particularly resistors inautomotive and related applications.

BACKGROUND

As electronics content in a typical vehicle has substantially increased,the demands on the battery and charging system of a typical vehicle havealso increased. Moreover, with the advent of the hybrid gas-electric carand all-electric cars the battery and charging system becomes an evermore vital part of a vehicle. An unhealthy electrical system in today'scar may jeopardize vital functions such as steering and braking.

Therefore, it has become essential for onboard computers to have sensoryinformation about the charge used, charge returned and charge availablefrom the battery and the overall health of the charging system. The mainsensor for this is a current sense resistor integrated into the batterycable.

Traditionally, this is a flat resistor made of a MANGANIN resistiveelement terminated by copper pieces welded or brazed to each end of theresistive element. MANGANIN is an alloy typically 86 percent copper, 12percent manganese, and 2 percent nickel which provides low resistance.This flat resistor would be located at the end of the cable adjacent tothe connector to the battery and would be surrounded by supportelectronics encased in a potted container. Such a resistor may also beused in applications other than automotive application such as, but notlimited to, galvanic plating power supply cables, welding cables, andother applications.

Therefore, it is a primary object, feature, or advantage of the presentinvention to improve over the state of the art.

It is a further object, feature, or advantage of the present inventionto provide a resistor suitable for use in automotive and relatedapplications where the resistor is connected to a cable.

Yet another object, feature, or advantage of the present invention is toprovide a resistor which allows current sensing.

One or more of these and/or other objects, features, and advantages ofthe present invention will become apparent from the specification andclaims that follow.

SUMMARY

According to one aspect of the present invention, a resistor includes asubstantially cylindrical resistive element having a resistance of lessthan about 1 mΩ, a substantially cylindrical first terminationelectrically connected to the resistive element, and a secondtermination electrically connected to the resistive element. Thesubstantially cylindrical first termination is hollow to allow foraccepting a connection such as from a battery cable. There may be one ormore sense leads attached to the resistor.

According to another aspect of the invention, a method of forming asubstantially cylindrical resistor is provided. The method includesforming a hollow cylindrical resistor body by rolling a flat sheetcomprising a resistive element and a first termination and a secondtermination joined on opposite ends of the resistive element.

According to another aspect of the invention, a method of forming asubstantially cylindrical resistor includes providing a first tube for afirst termination, providing a second tube for a second termination, andmagnetic pulse welding a resistive element between the first tube andthe second tube to thereby provide a substantially cylindrical resistor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one embodiment of a cylindrical resistorof the present invention.

FIG. 2 is an exploded perspective view of one embodiment of thecylindrical resistor of the present invention.

FIG. 3 is a perspective view of the cylindrical resistor connected to abattery cable assembly of a vehicle.

FIG. 4 is a perspective view of the cylindrical resistor connected to abattery cable of a vehicle.

FIG. 5 illustrates a step in the process of forming a cylindricalresistor according to one embodiment.

FIG. 6 illustrates a step in the process of forming a cylindricalresistor according to one embodiment.

FIG. 7 illustrates a step in the process of making a cylindricalresistor according to one embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is generally directed towards a cylindricalresistor and a method of making the cylindrical resistor. Thecylindrical resistor may be used in applications such as, but notlimited to, automotive applications, galvanic plating power supplycables, welding cables, and other applications. The cylindrical shapeallows the resistor to be integrated into a cable assembly in a morespace efficient manner and also allows insertion at any position alongthe length of the cable. Flexibility in positioning allows supportelectronics to also be positioned in a location closer to otherelectronics modules or at the battery terminal.

FIG. 1 illustrates a perspective view of one embodiment of a cylindricalresistor 10. The cylindrical resistor 10 includes a resistive element12. The resistive element 12 may be made from a cylindrical piece ofMANGANIN wire, or other suitable resistive material. Each end of theresistive material is terminated with copper or another suitableconductive material to form the terminals 14, 16 of the resistor 10. Theterminals 14, 16 may be used to connect the resistor 10 to the cableassembly and carry the main current. These terminals 14, 16 are attachedto resistive element 12 by welding, brazing or crimping. The terminals14, 16 may be capable of attachment to a battery cable assembly bywelding, brazing or crimping. The geometry of the terminals may varybased on the particular application for which the cylindrical resistoris used and the present invention is not to be limited by the specificgeometry of the terminals shown.

Integral to the attachment of these terminations there are one or moresense leads 22, 24 attached to the terminals 14, 16. These sense leads22, 24 are used for connection to support electronics that require asense voltage input in proportion to the electrical current passingthrough the resistor 10. These leads 22, 24 may be an extension of theresistor terminal material or may be otherwise added such as throughwelding, brazing, crimping, or other means. The specific geometry ofthese sense leads may vary according to specific applications andenvironments and the present invention is not to be limited to thespecific geometries shown.

In one embodiment, the assembly of this shunt resistor 10 consists ofcopper tubes for the terminations 14, 16 and a piece of a substantiallycylindrical MANGANIN resistance wire as the resistive element 12. Theresistance wire is cut to a short segment. One end of the segment ofresistance wire is placed in the end of one copper tube 18 and the twoare joined by a magnetic pulse weld that uniformly collapses the tubeonto the wire at such speed that a weld occurs. The other end of theMANGANIN wire resistive element is inserted into the end of the othercopper tube 20 and joined by another magnetic pulse. Thus, a resistorsuch as resistor 10 in FIG. 1 is formed.

The amount of unwelded resistive material between the ends of the twocopper tubes 18, 20 determines the blank resistance value. Adjustment ofthe resistance value may be made by a lathe, abrasion, or laseringoperation that reduces the diameter of the exposed MANGANIN wire or byremoving copper from the end of each tube effectively lengthening theMANGANIN resistive element. In addition, resistance may be adjusted byadding termination material (such as copper or other conductivematerial) back to the resistive element such as by welding. At thispoint, the open ends of the copper tubes 18, 20 are ready to acceptfurther processing steps to connect them to a cable assembly, such asinserting cable 34 into the open tube and magnetically pulse welding thetwo pieces together as shown in FIG. 4. This joint could also be made bysoldering, crimping, brazing or other welding methods. A battery postclamp 30 having an end 32 could also be inserted to one of the open tubeends and secured in place as shown in FIG. 3. The battery post clamp maybe secured by soldering, crimping, brazing, or other welding methods.

FIG. 5 and FIG. 6 illustrate another embodiment of a cylindricalresistor. In this embodiment, the resistor utilizes a flat resistiveelement of MANGANIN, or other suitable resistive material, with copper,or other suitable conductive material, terminals welded to each end ofthe resistive material in the same fashion as may be used in fabricatingpower metal strip resistors such as disclosed in U.S. Pat. No. 5,604,477to Rainer, herein incorporated by reference in its entirety.

In FIG. 5, a flat sheet 39 is shown. The flat sheet 39 includes aresistive material 42, and terminal material 40. The terminal materialincludes a first portion 40A and a second portion 40B on opposite sidesof the resistive material 42. Sense lead 22 is electrically connected toand extends from the first portion 40A of the terminal material 40 whilesense lead 24 is electrically connected to and extends from the secondportion 40B of the terminal material 40.

The flat sheet 39 is rolled into a cylinder with the resistive material42 becoming a band that curves around the circumference of the cylinderas best shown in FIG. 6. The resistive material 42 and terminal material40 may have holes or slots 46 in specified areas to facilitate the rollforming process and to facilitate crimping to a cable. These slots 46may also be used to adjust resistance value and TCR. The material fromthese slots 46 may be separated from the main body on three sides yetleft connected on the fourth side to form a sense terminal integral tothe resistor material.

In another embodiment, shown in FIG. 7, the resistor is configured toallow for one termination 40A to be cylindrical for attachment to acable while the second termination area 40B has a flat terminal 48 whichmay include an aperture 50. The flat terminal 48 may be connected to abattery post or other stud mount connector.

Note that when the cylindrical resistor is hollow, the resistive elementmay be cooled by circulating a fluid through it. Cooling may bedesirable in certain environments.

The cylindrical resistors of the present invention have resistancevalues less than 1 mΩ and are designed to handle current of 200 A ormore. Thus, the cylindrical resistors are well-suited to automotiveapplications, battery monitoring applications, and related applicationswhere a low resistance is desired.

Therefore, a cylindrical resistor has been disclosed. The presentinvention contemplates variations in the size, shape, materials used,resistance, and other variations. Although various embodiments are shownand described, the present invention is not to be limited to thespecific embodiments shown.

1.-24. (canceled)
 25. A resistor comprising: a cylindrical resistiveelement having a first end and a second end; a first terminal adjacent afirst end of the resistive element; a second terminal adjacent thesecond end of the resistive element; a first sense lead electricallyconnected to the first terminal and having at least a portion extendingaway from a longitudinal axis of the resistor; and a second sense leadelectrically connected to the second terminal and having at least aportion extending away from a longitudinal axis of the resistor.
 26. Theresistor of claim 25, wherein the first sense lead is positioned betweena central portion of the resistive element and an outer end of the firstterminal.
 27. The resistor of claim 26, wherein the second sense lead ispositioned between a central portion of the resistive element and anouter end of the second terminal.
 28. The resistor of claim 25, whereinthe first terminal comprises a cylindrical opening adjacent the firstend of the resistive element.
 29. The resistor of claim 28, wherein thecylindrical opening adjacent the first end of the resistive elementreceives at least a portion of the first end of the resistive element.30. The resistor of claim 29, wherein the first terminal has an openouter end configured to receive an external connection.
 31. The resistorof claim 28, wherein the second terminal comprises a cylindrical openingadjacent the second end of the resistive element.
 32. The resistor ofclaim 31, wherein the cylindrical opening adjacent the second end of theresistive element receives at least a portion of the second end of theresistive element.
 33. The resistor of claim 25, wherein the resistiveelement has a central opening.
 34. The resistor of claim 25, wherein theresistive element comprises a segment of resistance wire.
 35. Theresistor of claim 25, further comprising a flat terminal portion. 36.The resistor of claim 30, wherein the external connection comprises acable or battery post.
 37. A method of forming a resistor, comprising:providing a cylindrical resistive element having a first end and anopposite second end between a first terminal adjacent the first end ofthe resistive element, and a second terminal adjacent the second end ofthe resistive element; electrically connecting a first sense lead to thefirst terminal, at least a portion of the first sense lead extendingaway from a longitudinal axis of the resistor; and electricallyconnecting a second sense lead to the second terminal, at least aportion of the second sense lead extending away from a longitudinal axisof the resistor.
 38. The method of claim 37, wherein step ofelectrically connecting comprises positioning the first sense leadbetween a central portion of the resistive element and an outer end ofthe first terminal.
 39. The method of claim 38, wherein step ofelectrically connecting comprises positioning the second sense leadbetween a central portion of the resistive element and an outer end ofthe second terminal.
 40. The method of claim 37, wherein the firstterminal comprises a cylindrical opening adjacent the first end of theresistive element.
 41. The method of claim 40, wherein the cylindricalopening adjacent the first end of the resistive element receives atleast a portion of the first end of the resistive element.
 42. Themethod of claim 41, further comprising connecting an external connectionto an open outer end of the first terminal.
 43. The method of claim 40,wherein the second terminal comprises a cylindrical opening adjacent thesecond end of the resistive element.
 44. The method of claim 43, whereinthe cylindrical opening adjacent the second end of the resistive elementreceives at least a portion of the second end of the resistive element.45. The method of claim 37, wherein the resistive element has a centralopening.
 46. The method of claim 37, wherein the resistive elementcomprises a segment of resistance wire.
 47. The method of claim 37,further comprising a flat terminal portion.
 48. The method of claim 42,wherein the external connection comprises a cable or battery post.